1. Field of the Invention
The invention relates generally to compositions having a leachable organic compound distributed throughout a polymer matrix and to methods of controlling the leaching rate of the leachable organic compound from the polymer matrix. In particular, the invention relates to compositions having a leachable organic compound distributed throughout a fluoroepoxy-silicone amine polymer matrix.
2. Description of the Related Art
Coating compositions containing leachable biocides are used to protect surfaces in an aquatic environment from fouling from marine organisms. Antifouling coating compositions containing biocides are disclosed in U.S. Pat. No. 4,127,687 to Dupont, in U.S. Pat. No. 4,898,895 to Masuoka et al, and in U.S. patent application Ser. No. 08/251419, filed May 31, 1994, by the present inventors. With antifouling coating compositions, it is important that the biocide leach out of the coating at a fast enough rate to provide a concentration of the biocide on the coated surface sufficient to protect the surface against fouling by marine organisms. On the other hand, if the leaching rate is too fast, the biocide may leach out of the coating completely in a short period of time, after which the coating is ineffective and must be replaced. U.S. Pat. No. 4,127,687 and U.S. patent application Ser. No. 08/251419, filed May 31, 1994, teach that the rate of leaching can be controlled by selecting a biocide with the appropriate degree of solubility to achieve the desired leaching rate. However, this method of controlling the leaching rate restricts the choice of biocide to those that meet the solubility criteria. It would be helpful to have an antifouling coating composition wherein the rate of leaching of any biocide can be controlled by altering the polymer matrix.
U.S. Pat. No. 4,898,895 describes an antifouling paint comprising an antifoulant and a vinyl polymer or copolymer containing a trimethylsilyl group or a polydimethylsiloxane and states that the polymer or copolymer controls the antifoulant so that it does not dissolve in seawater either excessively or insufficiently. However, the patent does not disclose any method of achieving precise control over the leaching rate.
Controlled release matrices for the release of organic compounds are also found in other fields such as the medical field, where it is often desirable to provide for the controlled release of a drug into the bloodstream or body tissues. For example, U.S. Pat. No. 5,597,584 discloses a method of controlling the rate of release of a drug from a silicone rubber matrix by changing the crosslink density of the silicone rubber matrix.